Linking error on PPA for Ubuntu Cosmic 18.10; GLVND

Before this policy can be set to NEW it should be investigated whether Widelands can be compiled on Linux using the GLVND-libs. It seems not possible ATM:

https://code.launchpad.net/~widelands-dev/widelands/cmakepolicy/+merge/356018/comments/926483

This seems to contain some answers for the linking errors:

https://stackoverflow.com/questions/23729213/link-error-when-trying-to-build-a-simple-opengl-program

This still fails in the daily PPA for Ubuntu 18.10:

/usr/bin/ld: ../../graphic/libgraphic_draw_programs.a(fill_rect_program.cc.o): undefined reference to symbol 'glEnable'
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/8/../../../x86_64-linux-gnu/libGL.so: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status

Example log:

https://launchpadlibrarian.net/393322398/buildlog_ubuntu-cosmic-amd64.widelands_1%3A19-ppa0-bzr8888-201810150529~ubuntu18.10.1_BUILDING.txt.gz

I think it is better to continue here instead of the already merged proposal.

Ubuntu 18.10 comes with GCC 8.2.0 as default compiler.

I tested on Ubuntu 18.10 with GCC 8.2.0 and ran into the same issue. Using Clang 7 on the other hand worked like a charm.

kaputtnik tested the changes on his ArchLinux-box with GCC 8.2.1 and had no issues whatsoever.

I currently testing with GCC 7.3.0, but this might take some time.

Same problem with gcc 7.

I don't get it.

https://launchpadlibrarian.net/393526226/buildlog_ubuntu-cosmic-amd64.widelands_1%3A19-ppa0-bzr8890-201810161048~ubuntu18.10.1_BUILDING.txt.gz

-- Adding linker flags for GLVND.

When I test r8890 in my 18.10 virtual machine it does not set the flag, because it detects Ubuntu 18.10 proberly and sets CMP0072 to OLD. This apparently does not happen on the build server....

---

But I think I found the cause for the linker errors: It detects the following lib:

-- Found OpenGL: /usr/lib/x86_64-linux-gnu/libOpenGL.so

but later on it wants to use this one for linking: /usr/lib//x86_64-linux-gnu/libGL.so

/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/8/../../../x86_64-linux-gnu/libGL.so: error adding symbols: DSO missing from command line

oO

The GNU linker is somewhat weird... I have a similar issue on macOS when using GCC 7. There it links the wrong ASAN-libraries.

Create a branch which has all needed variables printed out and see what values are produced on the build server?

Maybe it is easier to have a compile option USE_GLVND which defaults to OFF?

The PPA is still red: https://launchpadlibrarian.net/393583865/buildlog_ubuntu-cosmic-amd64.widelands_1%3A19-ppa0-bzr8890-201810161817~ubuntu18.10.1_BUILDING.txt.gz

The problem is that "lsb_release" is not available on the build-server... for some reason. That's why it works in my VM, but not on the build-server.

I do have another idea, though.

Does some system variables also not work?

https://code.launchpad.net/~widelands-dev/widelands/GLVND_18_10/+merge/356771/comments/928588

You could set up your own PPA on the branch, there is a button in the branch view. Copy over the code from trunk and you should be able to request builds manually for testing.

Party on:

https://code.launchpad.net/~widelands-dev/+recipe/widelands-daily

Tadaa!

Thanks :)

Fixed in build20-rc1